Twins manager Paul Molitor said Monday he had been told Castro could miss four-to-six weeks. Dr. Richard Steadman is to operate in Vail, Colorado.

“We know he has a history, then he tweaks it, then it feels good, and eventually it starts flaring up again and you try to find out what’s going on,” Molitor said. “Finally, between different people talking over, analyzing his history and himself, and images that they were able to get through testing that this was probably the right thing to do.”

The 30-year-old Castro has been on the disabled list since May 5. Castro is hitting .143 with three RBIs in 19 games and tried to play through knee pain for the previous few weeks.